North America is a massive continent.
Built from a combination of different parts of the earth’s crust. It is amazingly diverse in composition and tells a story of how the continent came to be.
Anyone that has traveled across North America whether it be Canada, Untied States or Mexico can tell you that is a long trip. It is a journey not of hours but days and weeks. Along the way an observer will pass many different types of landscapes and environments which all tell a fascinating story of collision and chaos.
In this blog we discuss the formation of the western coast of North America and how all of these diverse regions came to be.
Surrounded by the Pacific, Atlantic and Arctic oceans, the continent has been isolated from the rest of the world for a long time. It was the last place to be explored by Europeans and was the last frontier of exploration. The west coast of North America to this day remains an isolated and untouched region in many parts.
There are vast distances spanning huge portions of complete wilderness all throughout the continent. Up north in Canada and Alaska is where this can be seen at its most extreme. There are sections of the land where you can travel many hundreds of kilometers or miles and see no sign of civilization. The abundance of lakes, rivers, forests and mountains ranges can be a mind-numbing experience.
North America is a land that is still changing and will continue to do so for many millions of years into the future. Sculpted by fire and ice, it has formed a diverse range of climates which range from arctic tundra to southern desert near the equator. The actions of volcanoes, glaciers, titanic rivers and lakes have all played a role in the creation of the landscape.
There are mountain ranges such as the Cascades, Rockies, Seirra Nevada, Coast, St Elias, and many other sub ranges. These mountain ranges form the backbone of north America and stretch all the way up the spine of North America from Mexico to Alaska and Nunavut in Canada. Each was formed through various geological processes.
The accretionary belt of North America stretches along the pacific coast of North America. It is a series of geological terranes which have progressively been welded to the continent over hundreds of millions of years.
A terrane is a distinct composition and combination of the earth’s crust which has been separated from other portions.
It is a block of crust that has been separated from other contiguous pieces and becomes welded to other sections through tectonic processes. These tectonic process merge the various terranes together through the subduction and rifting of the earth’s crust.
Subduction is the process of a thinner tectonic plate sliding under a thicker tectonic plate. The Jaun de Fuca plate subducting under the North American plate is an example of this. This process causes the Juan de Fuca plate to burn off below the in the earth as this as happens it creates magma from burned off rocks and elements. This travels up with gases and forms magma chambers which bulge out and form mountains. This is the process which has created the volcanoes of the Cascades such as Mount Rainer, St Helens, Adams, Hood, and many others.
This subduction process also pushes the surface islands and land attached to the pacific plate toward North America which causes it to collide into North America over many millions of years. The plate moves toward North America gradually 3” to 4” every year which causes islands like Hawaii to drift towards the Pacific coast of North America. This has been happening for hundreds of millions of years.
It is a repetitive process that has caused the continent to grow. Entire new regions have been formed and sculpted over the many different eras of time. Each period from the Cretaceous to the Holocene to the present has had its own events which characterize the various geologic formations and conditions.
Volcanoes play a critical role in the process; the eruptions provide lava in huge quantities which flows out to create many different landforms. Overtime a combination of wind, rain, sun and weather chisels and carves the terranes into the iconic features which we see.
But things where not always like this and they will not stay the same for long. Ever since the earth began 4.6 billion years ago it has been undergoing dynamic changes which have been a continuous process.
Ancient continents that have long been ripped apart by various tectonic forces have brought about new continents some of which exist today. Ancient oceans and seaways used to exist, the Pacific and the modern of oceans of the world are relatively new.
Geologic time takes place on a massive scale, it is hard for humans to comprehend.
We live such short periods relatively speaking. 100 yrs are mere minutes for volcanoes, mountains and other geologic forms. The sculpting of land is gradual one and something that we will not have the privilege of seeing with the exception of natural disasters.
These terranes for all the beauty and unique features also contain the potential for unlocked riches in mining and gems. These terranes that have fused to North America have come from all over the earth. There could be various valuable mineral formations waiting to be discovered. The terranes of Stikinia, Wrangellia, Quesnellia and others present a lot of mining potential that has been explored and is having steps taken to be explored further. These are a few examples of terranes that over time have traveled via subduction to the growing coast of north America where they become fused and join the continent.
What is the cause for all of this? There is a ridge out in the middle of the Pacific Ocean which is pushing the Pacific Ocean plate in two directions toward Asia and North America. This is creating the infamous ring of fire which causes the formation of volcanoes all along this subduction zone. The ring of fire causes many volcanic eruptions, earthquakes, tsunamis and other hazards.
The Pacific Ocean is full of volcanic islands such as the Hawaiian Islands and the Aleutian Islands in Alaska. These volcanic islands punch up right out of the oceans and typically take the form of stratovolcanoes.
Hotspot or mantle plume volcanism is a huge part of this process which causes the formation of new islands in different locations as the pacific plate that moves over top the mantle plume. The mantle plume of the hotspot pushes up on the crust and forms volcanoes due to the magma rising up and trying to escape. Yellowstone in the United States is a famous hotspot super volcano. There is also an extinct super volcano up in Canada on the Ontario and Quebec border.
Continental rifting is also something to consider, up in northern BC and the southern coast of Alaska it plays a pivotal role in the formation of many shield volcanoes. The pulling apart of the plates causes a rift to open which allows lava to flow up and form into a shield volcano. The northern BC region is a very geologically diverse region that will be covered in other blogs.
Geology is history, it tells the story of how the earth came to be and the various processes that played a role in forming them. Exploring these various locations is an exciting and engaging experience that allows you a glimpse of the past.
Traveling North America is no small undertaking and one could spend a lifetime searching to unlock the secrets of this magical place and what was the last frontier on planet earth!